Hello!
I am going to my mom's house to assess the situation but she tells me one of her toilets was leaking around the base. I have seen from some past posts that there may be a number of causes, i.e. wax ring offest, drain pipe filling with water above the wax ring, etc. Until I can see the problem first hand I won't be sure what I'm dealing with. My mom tells me that a flooring installer told her the wood under the toilet was bad... which means a can of worms for me:o. That said, I may have to remove the flange and replace the bad subfloor and then replace the flange. I have found a series of steps to accomplish this, but have some questions...

Removing the flange steps state that you must 'cut off the flange at the red line from inside the pipe with a dremel' There is no other mention of the 'red line' in the steps and I am unsure what this refers to, any ideas?
<at this point I would remove and replace the bad subfloor>
Then it states to fit the coupling onto the pipe that you cut off in the floor and fit the new pipe length into the coupling and mark on the new pipe to the correct height which is just below floor level. How much below floor level will it need to be to ensure the flange is flush when installed in a later step? It then states to remove the pipe and coupling and cut it with a hacksaw to the correct length.
I understand that we have to cut the pipe from the inside because the flange is cemented to the pipe, but I want to be sure to replace the pipe with the proper length of new pipe to ensure a successful repair. Any advice on what the term red line means when cutting and removing the old pipe and exactly how far 'just below floor level' is in order to cut the new pipe off will be most appreciated.

First, lift the toilet and assess the damage. Maybe, you don't have to deal with subfloor at all.

First you can't know the best repair approach until you have seen the situation and determined just what the problem is.

Sounds like you will be replacing damaged sub flooring. That can be done with out removing flange. Take a look and post back. Pictures will be a big help. Replacing sub flooring is easy but will probably require re-tileing assuming tile floor covering.

Thank you Milo,

This is what I'm hoping for - I was just trying to prepare for the worst and do as much research as I can in advance since there is no internet access at mom's house and she lives over an hour from me. The toilet is out currently as the flooring installer had removed it previously. Mom tells me the floor 'dishes' down near the toilet. Aren't there flange repair kits with a plate that can level up an uneven surface like that?

Thanks again!

If there is a small dip, you still can reset toilet and it will work fine. Just make sure you attach flange to the subfloor well with brass/galvanized screws. Install brass bolts. Then install tall wax ring with flange and toilet over it. Feel the toilet when you are lowering it over the wax ring. You want to feel the toilet as it touches the wax ring and then as it pushes it down a bit. If you don't feel compressing wax ring, you may want to ad another, skinny, wax ring. Then, reset toilet again.

Thank you Harold,

I will take my digital camera out with me. I was kind of wondering if the subfloor could be replaced without removing the flange! If it is really rotten wood it should come out pretty easily. Would you advise I replace the subfloor without removal of the flange in two pieces, i.e. two halves with a nalf circle cut out of each to match up around the drain pipe and slide under the flange? The flooring is linoleum so no problems there... I appreciate your assistance!

Yes, photo would be great help. Maybe you can post directly from your phone...

Yes, you would cut out damaged sub flooring to next joist on either side. Replace with two pieces with a cut out for pipe. If you have both a sub flooring and flooring (3/4 ply sub flooring with 1/2" flooring) you would repeat with joint running in the opposite direction.

Great! I believe it is 3/4" ply but it doesn't sound like there's anything on top of that (other than the linoleum). I am heading out there now and will update once I'm back online. Thank you Milo and Harold for all your advice!